1. Field of the Invention
The present invention relates to foam-dispensing pump containers for discharging, from a foam discharge opening, foam produced by mixing a foamable liquid in the container body and air when a nozzle head is pushed down, and more specifically, to an improvement for preventing usability from being degraded by the liquid or foam flowing backward into the pump after foam is discharged.
2. Description of the Related Art
A variety of configurations have been conventionally proposed for foam-dispensing pump containers that produce foam by mixing a foamable liquid contained in the container body and air drawn into the container from the outside and that discharge the foam from the container to the outside through a foam passage inside a nozzle head, when the nozzle head of a nozzle body provided at the top of the container is pushed down. In those conventional foam-dispensing pump containers, the nozzle head can generally move up and down together with a liquid piston and an air piston.
When the nozzle head moves up, the liquid piston, which is in sliding contact with a liquid cylinder, rises to draw the foamable liquid from the container body into a liquid chamber, and at the same time, the air piston, which is in sliding contact with an air cylinder, rises to draw air into an air chamber from the outside. Then, when the nozzle head moves down, the liquid piston is lowered to bring the foamable liquid into an air-liquid mixing chamber from the liquid chamber, and at the same time, the air piston is lowered to bring air into the air-liquid mixing chamber from the air chamber. The foamable liquid and air brought into the air-liquid chamber are mixed to a foam, and the produced foam is discharged from a foam discharge opening provided at the downstream end of the nozzle head portion.
In those conventional foam-dispensing pump containers, the liquid or foam remaining in the air-liquid mixing chamber sometimes flows backward into an air passage between the air-liquid mixing chamber and the air chamber. The liquid or foam flowing into the air passage dries and solidifies, and narrows or blocks the flow path, causing problems concerning usability of the foam-dispensing pump container, such as lower foam quality caused by a reduction in the amount of air that can be supplied to the air-liquid mixing chamber, or an increased force required to push down the pump.
In view of the problems described above, a foam-dispensing pump container proposed in Japanese Utility Model Registration No. 2581644 can prevent the residual foam or liquid from flowing backward into the air passage from the mixing chamber by providing a rod-shaped valve body having an almost funnel-shaped latch portion in its upper end to close both a liquid chamber outlet on the mixing chamber side and an air passage outlet on the mixing chamber side at the same time. Since foam-dispensing pump containers are generally configured to discharge foam when the nozzle head is lowered, both the liquid chamber outlet on the mixing chamber side and the air passage outlet on the mixing chamber side are left open while the nozzle head is at the bottom dead center. In the foam-dispensing pump container proposed in Japanese Utility Model Registration No. 2581644, after the nozzle head starts rising from the bottom dead center, the rod-shaped valve body closes the air passage outlet on the mixing chamber side and the liquid chamber outlet on the mixing chamber side simultaneously. When the nozzle head starts rising again from the bottom dead center, the liquid chamber and the air chamber increase in volume and are consequently depressurized temporarily. Therefore, in the foam-dispensing pump container proposed in Japanese Utility Model Registration No. 2581644, the residual liquid or air may flow backward into the depressurized air passage or air chamber from the mixing chamber from when the nozzle head starts going up until the rod-shaped valve body closes the liquid chamber outlet on the mixing chamber side and the air passage outlet on the mixing chamber side.